Electric switch



G. A. BURNHAM June 2, 1925.

ELECTRIC SWITCH Filed March 51. 1919 3 Sheets-Sheet 1 June 2, I925. 1,540,596

G. A. BURNHAM ELECTRIC SWITCH Filed March 31. 1919 3 Sheets-Sheet 2 1 level June 2, 1925.

G. A. BURNHAM ELECTRIC SWITCH Filed March 31 1919 3 Sheets-Sheet 3 OrZLeaeZ 1. 1: 4.4. 1. i f v all LEI/62 I21 pentort Patented June 2, 1925.

UNITED "STATES 1,540,596 PATENT oF FicE.

GEORGE A. BURNHAM, OF SAUGU'S, MASSACHUSETTS, ASSIGNOR, BY MESNE ASSIGN- "MENTS, TO CONDIT ELECTRICAL MANUFACTURING COMPANY,

MASSACHUSETTS.

A CORPORATION OF ELECTRIC SWITCH.

' Application filed March 31, 1919; Serial No. 286,353.

To all whom it may concern:

Be it known that I, GEORGE A. BURN- HAM, a citizen of the United States, and resident of Saugus, in the county of Essex and State of Massachusetts, have invented an Improvement in Electric Switches, of which the following is a specification,

This invention relates to oil immersed electric switches of relatively large'currentcarrying capacity and more particularly adapted for the control of alternating current circuits. a

The object of my invention is in theprovision of means whereby the current-carrying capacity ofa switch of the above-described type may be governed and whereby a switch having relatively moderate physical dimensions may have a relatively great current-carrying capacity.

The ability of an electric switch to continually conduct currentlis limited by its temperature, and consequently the temperature rise of its components, due to thefheating effect of the current conductedf p The heating of an oil immersed switch emanates from two main sources; the current-conducting components and the oil'receptacle. The heating of the current conducting components is a function oftheir resistance, frequency of the current and shape of the alternating wave, as well as value of current. The heating of the oil receptacle is a function of the magnetic permeability of the material composing the receptacle, the frequency of the alternating current and the form of the alternating I wave, as well as strength of current.

Heating of the current-conducting compo nents may be decreasedv'by providing a relatively great mass of conducting material, thereby decreasing theresistance of such components and byproviding largesurface thereby increasing the heat dissipating effect of the components and reducing hysteresis and eddy current losses due to the alternating current and possible abnormal wave forms thereof. i p

Heating of the oil receptacle may be decreased by decreasing the magnetic permeability of the material composing said receptacle as by forming said tank ofnonmagnetic ,material and thereby decreasing hysteresis and eddy current losses therein by decreasing the magnetic effect of the current or by laminating the receptacle, an impract cal proceeding. a

There is a limit to thedecrease in heating in the current conducting components of the switch by the above methods beyond which it is not commercially practicable to go because of the relatively massive and expensive resulting structure and with comparatively little resultant increase in ourrent-carrying capacity.

There is also a limit to the decrease in heatingin the oil receptacle by theabove methods beyond which it is not commercially practicable to go and'for similar reasons. j

The means I employ to provide for the governing of the current-carrying capacity of an electric switch and to provide a switch having relatively'moderate physical dimensions with a relatively great current-carry ing capacity is in the artificial or forced cooling of theswitch or the heated components thereof and which broadly shown and described in my Patent No. 1,337,995, dated April 27, 1920. l

A further object of my invention is in the association of artificial cooling, means with an oil switch having a removableoil recepadapting the current-carrying capacity of the independent switches of the apparatus to be independently governed and increased.

In carrying out these objects of my invention I arrange a cooling coil in the oil receptacle and preferably adjacent the walls thereof. I extend the ends of said coil through the walls of said receptacle and provide means whereby said ends may be detachably and removably associated with a cooling medium circulatory system whereby the oil receptacle with cooling coil may be removed from the switch when desired.

A further object of my invention is a coolingattachment for existing oil switches and which may be applied thereto without alteration to the switch structure to thereby provide the switch with an increased current-carrying capacity.

In carrying out this object of the invention'I form an oil receptacle and cooling means, as a coolingcoil, as a complete unit which is adapted to replace the usual oil receptacle of the switch and be removably received on the switch frame whereby the switch, without other change, is conditioned for an increased capacity.

It it obvious that any cooling medium may be employed and forced through the cooling coil but I prefer, under ordinary circumstances to employ water at normal ten'ipera ture as the cooling medium because of its abundance, convenience and cheapness. Under normal or unusual conditions, however, it is obvious that any cooling medium andsystem may be employed.

The current-carrying capacity of a switch provided with artificial or forced cooling means may be conveniently governed by varying the rate of flow of cooling medium in the cooling coil, or by varying its cooling effect. I

The oil utilized as the circuit-interrupting medium is also utilized as a heat conveyer to conductheat from the heated components to the cooling coil.

Certain features of this invention are disclosed in my co-pending application, Serial No. 300,557, filed May 29, 1919.

Fig. 1 is a side view of a multi-phase switching unit embodying my invention.

Fig. 2 is a vertical section along lines 2-2 of Fig. 1.

Fig. 3 is a plan View of the oil receptacle with cooling coils in a detached position.

Fig. t is a section along lines 33 of Fig. 3.

Fig. 5 is a sectional detail showing a modified arrangement of oil receptacle, cooling coils and tank lining.

Fig. 6 is a detail of an end connection for a pipe coil.

I have :chosen for the purpose of illustrating my invention the type of switch shown and described in my patent application Serial No. 240,317, filed June 17, 1918. The switch comprises a back-bone 10 formed as a hollow rectangular box structure in which the switch operating mechanism is arranged. Supporting plates 11 formed of channel iron or similar construction are secured to each end of the backbone and are clamped by the U-bolts 12 to the pipe uprights 13 forming components of the switch-supporting frame. Said back-bone is also intermediatcly supported betweenth'e switch units by the upright supporting posts 1 1.

As here shown, the switch is adapted for the control of a three-phase line and three independent units are therefore shown.

Each switch unit comprises a switch-frame or plate 15 secured to the under side of said back-bone by the bolts 16. An oil receptacle 17, preferably formed 'ofs'he'etsteel, depends from said'switch frame and is secured thereto by the bolts "18 which pass through the mass side walls of channel-members 19 secured to walls of the receptacle and through bosses 20 of the switch frame to which they are detachably secured by the wing-nuts 21.

Insulators 22 extend through openings in the switch-frame and two sets of conductingbars 23 and 23 are extended therethrough. Each set of bars forms an independent switch stud and, in cooperation with independentbrush-members forms the equivalent of two independent switches, although electrically the pairs of studs are connected to form a single pole of the switch. The bars 23 and 23 are spaced from each other by spacing blocks 21 whereby a. laminated switch-stud structure is formed. Said bars are clamped between the clz'unping-mei'nbers 25 and 26 by which they are also secured to the insulating bushings 22. Said clamping member 26 is made of electrically conducting material and it is designed to carry a certain percent of the current carried by the switch to thereby serve as an equalizer between the two switch studs and provide substantially uniform current distribution therebetween regardless of variations of brush pressure. The switch studs terminate within the oil receptacle in independentstationary contact-men'ibers 28 with which the movable switch members engage.

The movable switch members comprise the brushes 29 supported by the insulating rods 30 which in turn are independently and adjustably secured to a switch opera-ting bar 31 by which all of the switches are conjointly operated.

Similar toggle members 32, individually pivoted at to the switch frames 15, serve to move said bar upward said switch-frames to move the movable switch members into switch-closed position. Said rod 31 is guided in its vertical movements in a straight line by means of the guide bearings 31 movable within the guide bars 34 as is more clearly shown and described in the above mentioned application. A rod is connected to said toggle members 32 and extends to operating means, not shown. A movement of said rod to the left, Fig. 1, acts to straighten all of said toggles and raise said bar 31, thereby to close the switch; and a movement in the opposite direction acts to break the toggle and permit the switch to open.

Each oil receptacle with which lily invention is associated is provided with handles 37 and lugs 38, (see Fig. 3) to which a tank raising and lowering device is adapted to be connected for the raising and lowering of the tank to and from position.

The switch, as abovc-described, is substantially as shown in the application above referred to.

The artificial cooling means associate-' with the switch and by means of which when necessary.

my invention is performed, includes a cooling coil 40 formed of a number of spacedapart convolutions of a fluid conductor or plpe having heat conducting walls; Said cooling coil is supported in said oil receptacle by upright member 41v arranged preferably at the corners of the receptacle and said convolutions are secured to said uprights by the strips 42 which are formed with recesses in which the separate convolutions are received. By supporting said coil adjacent the corners or bends thereof a mechanically strong and rigid structure is provided which requires no further or intermediate supporting means although it is obvious that such means may be provided The cooling coil is arranged in the upper part of the oil in the oil receptacle Where the temperature is the most elevated whereby the coil will most efficiently function to abstract the heat generated in the switch components. -The convolutions of the coil may extend downwardly as far aS desirable but there appears to be no necessity for extending the convolutions of the coil much below thestationary switch members and the brush members as the oil therebeneath is not appreciably elevated. It is very desirable, however, that no part of the cooling means or the coil, be above the oil level for, in such event moisture always present in the air in the oil receptacle would condense on the relatively cold coils and commingle with the oil and destroy the insulating properties thereof.

A tank lining comprising the bottom wall 45 and the sidewalls &6 arranged in box form is disposed at the bottom of the oil receptacle and is adapted to more or less snugly engage the walls of said receptacle. it is customary to provide a tank lining in this type of switch to-prevent an abnormal circuit interruptingarc from directly contacting with the wall of the oil receptacle and thereby grounding the electric circuit.

Said uprights 41 by which the cooling coil 40 is supported are secured to the walls 46 of said tank lining by the screws 47 and a solid unitary structure of cooling coil and tank lining is thereby provided. The supports for the cooling'coil. are preferably so arranged that the convolutionsthereof are spaced a substantial distance from the walls of the oil receptacle to thereby permit the free circulation of oil over said coils and between said coils and the wallsof said oil receptacle whereby-said walls are efiiciently and rapidly cooled as well as the current-conducting components of the switch.

The ends of the cooling coils are e2:- tended near the top and bottom of the oil receptacle through openingsal) in the tank and nipples 50 which are preferablyiwelded to the walls of said receptacle. Said open ings or passages 49 in said bushing are preferably somewhat larger than the diameter of the pipe composing the cooling coil whereby the end of said coil may be freely inserted theretnrough. A reducing bushing 51 preferably of a material similar to that composing the cooling coil is secured over said nipple 50 and the end of the pipe forming the cooling coil is extended therethrough and peened over as at 52 and soldered or brazed thereon.

The structure above described is nee-e"- sary for the reason that the ends of the cooling coil cannot be satisfactorily directly Welded or brazed to the walls'of the oil receptacle or to the nipple 50 as said oil receptacle and coil are formed of dissimilar materials, the receptacle being preferably of steel and the coil of brass or copper. The nipple 50 is therefore formed of iron or steel and may be readily welded to the receptacle walls, and the bushing 51 is formed of brass or copper and heend of the cooling coil may be readily brazed or soldered thereto, and by screwing said bushing over said nipple a satisfactory connection is formed.

A conductor for the cooling medium as water, is extended below the oil receptacle and preferably atone side thereof and separate risers 61 are extended upwardly therefrom, as is shown more clearly in Fig. 2 for connection with the cooling coils- Each riser is provided at its upper end with a control valve 62 by means of which the flow of water may be regulated whereby the current-carrying capacity of the switch may be governed. Said valve 62 is connected to the coil inlet through the coupling 63provided to permit the disconnection of the oil receptacle from the inlet pipe or riser for the removal of the receptacle.

The cooling coil outlet near the top of the oil receptacle is provided with a downwardly directed nozzle 65 which is so shaped as to insure a quiet flow of cooling medium as water therefrom. v

As here shown no provision is made for the control of the discharge of water from the outlet nozzle but such provision may be made if desired.

A trough 66', for the heated waste water, is extended to one side of and between the oil receptacles and the risers 61, and beneath the discharge nozzles 65. Said trough comprises a pipe having openings 67 therein at the top and under said nozzles through which water may pass from said nozzles into the pipe or trough.

Said pipe or trough is adapted to be of a capacity suliicient to receive without overflow the maximum amount 'of' cooling water that may be forced through the cooling coils and it is pitched in a direction toward its outlet or discharge pipe 69 to which it may 3 be connected by the elbow 68. A pipe bracket is secured to the oil receptacle of the intermediate switch of the switching unit and has a retlexed end 71 in which the trough is received when in position beneath the discharge nozzles (39. T 0 permit the removal of the oil receptacles the trough (it) is adapted to be swung on its threaded connection with the discharge pipe (39 away from said oil receptacle and the supporting member 70 is adapted to be made sulliciently resilient to permit this swinging movement and yet securely support the trough in position beneath the discharge nozzles.

Each tank, as is common practice, is provided with an oil gage 7 5 by means of which the oil level therein may be seen. A thermometer is also provided which has its bulb extended into the oil within the oil receptacle and adjacent the surface thereof, whereby the temperature of the switch may be known. Said thermometer is arranged on the side of the oil receptacle provided with the water controlling valves 62 whereby the rate of flow of cooling water may be determined and regulated.

In the removal of an oil receptacle the flow of water or other cooling medium in the cooling coils is first stopped in the cooling coils of all switches by the closing of the valves 62. The trough 66 is then swung away from the switches and couplings .63 are broken. There being no further obstruction to the downward movement of the oil receptacle, the tank supporting bolts 18 are removed and the tank may be lowered by any convenient means.

It is to be noted that the direction of flow of the cold cooling medium in the cooling coil is from the bottom of the oil to the top of the oil or it enters the cooling coil at the point where the oil is coldest and leaves the cooling coil in heated condition at the point where the oil is hottest.

There are two main sources oi": heat in the switch; namely, the current-conducting components and the walls of the oil receptacle. The cooling coils are arranged adjacent the receptacle walls and therefore a downward convection current in the oil is set up between the walls and the coil and heat is abstracted from the walls which thereby be come cooled. The heated oil from adjacent the current-conducting components of the switch risesto the surface of the oil and circulates to, and down over, the cooling coils and has its heat abstracted and the cold oil from which the heat is abstracted circulates about the heated current-conducting components and becomes heated and rises to pass through another heat abstracting cycle.

The temperature rise of the switch components may be largely controlled by controlling the rate of flow of cooling medium through the cooling coils.

coil to the uprights 41, in which position it is interposed between said coil and the current-conducting components of the switch. Said insulatin shield is preferably extended substantially fielow the top of the tank lining and spaced therefrom to provide adequate protection for the cooling coil and provide a passage for the flow of oil from the cooling coil into the main body of oil in the receptacle. The insulating shield is preferably, and as shown, spaced from the cooling coil whereby the entire surface of the coil may be utilized for cooling el'lect.

The top of said insulating shield is adapted to terminate a substantial distance beneath the surface 01' the oil in the receptacle whereby free circulation of oil about the cooling coils is provided.

The oil receptacle with associated cooling coil is adapted to be used as an attachment to existing electric switches to increase the capacity thereof. For this purpose, it is merely necessary to remove the oil receptacle with which the switch is originally provided and replace it with the above described oil receptacle with incorporated cooling coil. No other changes to the switch structure are necessary. By such inexpensive arrangement existing switches may have their capacity increased.

1 claim:

1. A multi-phase switching apparatus comprising an independent switch for each phase, each switch having certain inherent current-carrying capacity by virtue of its dimensions, and means to independently govern the current-carrying capacity of the switches comprising the switching apparatus.

2. A multi-phase switching apparatus comprising an independent switch for each phase, each switch having certain inherent current-c-arry1ng capacity by virtue oi its (llIIlEllSlODS, and means to independently augment the current-carrying capacity of prising a supporting frame, stationary and said receptacle to said switch permitting its removal therefrom, and switch cooling means removably associated w1th said Oll receptacle.

5. An oil immersed electric switch C0111".

prising a supporting frame, stationary and movable switch members depending therefrom, an oil receptacle enclosing said switch members, and adapted to contain oil in which said members are immersed, means securing said receptacl to said switch permitting its removal therefrom, cooling means associated with components of the mitting its removal therefrom, and a:cool mg coil associated with sa1d switch carried by said oil receptacle through which a cooling medium is adapted cool the switch.

7. A forced capacity electric switch comprising stationary andmovable switch members, an oil receptacle adapted to contain oil in which said members are immersed, a switch-cooling coil immersed in the oil in said receptacle, and means to govern the circulation of said cooling medium to thereby govern the current-carryingcapacity of the switch. a

8. A forced capacity electric switch comprising a switch frame, stationary and movable switch members depending therefrom, an oil receptacle adapted to'contain oil in which said switch members are immersed, a cooling coil arranged within said oil receptacle, means to support said coil by said receptacle, and means to connect said cool ing coil to a supply of coolingfiuid.

9. A forced capacity electric switchcom prising a switch frame, stationary and movable switch members depending therefrom, an oil receptacle adapted to contain oil in which said switch members are immersed, a cooling coil arranged within said oil re ceptacle, means to support said coilby said receptacle, said coil having its terminal portions extended through the walls of said oil receptacle beneath the oil level therein, means to seal said oil receptacle at such extended terminals of said cooling coil against escape of oil therefrom, and means removably to connect said terminal portions of said coil to a supply of cooling fluid,

to be circulated to 10. A forced capacity electric switch comprising a switch frame, stationary and movable switch members depending therefrom. an oil receptacle adapted to contain oil in which said switch members are immersed, a

switch cooling coil arranged in said oil receptacle having its convolutions adjacent the walls of said receptacle. the terminal portions of said coil extended through the walls of said oil receptacle, means to support said coil, and means removably to conmeet the extended terminal portions of said coil to a source of cooling fluid. I

11. A forced capacity electric switch comprising a switch frame, stationary and movable switch members depending therefrom, an oil receptacle adapted to contain oil in which said switch members are immersed, a cooling coil immersed in the oil in said receptacle to cool the same, and means to support said cooling coil in the top part of said oil receptacle beneath the surface of the oil therein.

12. Inan electric switch an oil receptacle having bottom and side walls, a cooling coil arranged therein in proximity to the walls thereof, means supporting said coil in the receptacle, end-portions of said, coil extended throughthe walls of the receptacle, means sealing said end-portions and receptacle against escape of oil from the receptacle, means removably to connect said end portions to a circulatory system for a cooling medium, and means to secure the receptacle and associated elements removably to a switch.

- 13. In an electric switch having stationary andv movable switch members, an'oil re-.

ceptacle adapted to contain oil in which said switch members are immersed, a cooling coil adapted for the circulation of a cooling medium arranged within the receptacle having' external inlet and outlet terminals, means to support said coil within said receptacle, and means to removably secure said receptacle with cooling coil to the switch.

14. A cooling attachment for electric switches comprising an oil receptacle, heat abstracting means associated therewith, and means to removably secure said attachment to a switch.

15. A forced capacity device for electric switches comprising an oil receptacle, heat abstracting means comprising a cooling coil adapted for the circulation of a cooling medium .therethrough carried by said receptacle, and means to removably securesaid der vice to a switch. a

16. An attachment for electric switches, comprising an oil receptacle adapted to contain oil in which switch components are immersed, a coolingcoil adapted for the circulation of a cooling medium therethrough having its convolutions arranged in proximi-ty to the walls thereof, said coil disposed near the top of the receptacle, and an insulating lining covering the bottom and the lower part or the side. walls of said receptacle, and means to removably secure said attachment to a switch.

17. Anattachment for electric switches, comprising an oil receptacle adapted to contain oil in which switch components are immersed, a cooling coil adapted for the circulation of a cooling medium therethrough having its convolutions arranged in proximity to the walls thereof, said coil disposed near the top 01' the receptacle, and an insulating lining covering the bottom and the lower part of the side walls of said receptacle, means to support said coil from said lining and means to removably secure said attachment to an electric switch.

18. An attachment for electric switches, comprising an oil receptacle adapted to contain oil in which switch components are immersed, a cooling coil adapted for the circulation of a cooling medium therethrough having its convo'lutions arranged in proximity to the walls thereof, said coil disposed near the top of the receptacle, and an insulating lining covering the bottom and the lower part of the side walls of said receptacle, uprights carried by and extended above said lining, means to support said coil by said uprights and means to remov ably secure said attachment to an electric switch.

19. An attachment for electric switches, comprising an oil receptacle adapted to contain oil in which switch components are immersed, a cooling coil adapted for the circulation of a cooling medium therethrough having its convolutions arranged in proximity to the walls thereof, said coil disposed near the top of the receptacle, and an insulating lining covering the bottom and the lower part of the side walls 01 said re-. ceptacle, uprights of an insulating material carried by and extended above said lining, means to support said coil by said uprights and means to secure said attachment to an electric switch.

20. In an electric switch having stationary and movable switch members, an oil receptacle adapted to contain oil in which said members are immersed, an insulating lining arranged therein and spaced from the walls of the receptacle, the top of said lining adapted to be below the level of oil in the receptacle, a cooling coil arranged in the space between the walls of the receptacle and the lining, and a passageway for oil through said lining near the bottom of the receptacle.

21. In an electric switch comprising movable and stationary switch members, an oil receptacle adapted to contain oil in which said members are immersed, a, lining of insulating material arranged in said receptacle and spaced from but adjacent the side walls of the receptacle, the top of said lining arranged a substantial distance below the surface of the oil in said receptacle, openings through the lining near the bottom thereof for passage of oil from the space between the walls of the oil receptacle and the lining to the main body of oil in the receptacle, said arrangement constituting a circulatory system for the cooling of oil in the receptacle.

22. An electric switching apparatus comprising a supporting standard, a plurality of switches supported thereby, each having oil receptacles removably secured thereto, a cooling fluid circulatory system associated therewith, each oil receptacle having a fluid inlet conductor removably connected with the system, and a fluid outlet conductor terminating in a nozzle portion, and a trough associated with said system removably retained in position beneath said nozzle-portions adapted to receive hot cooling medium from the oil receptacles.

23. An electric switch having means to determine the electrical operating characteristics thereof, comprising means to measure the temperature of the components thereof, and means to vary said operating characteristics comprising means to cool said components, and means to vary the cooling efi'ect.

2 An electric switch having an oil re.- ceptacle, relatively-movable switch-members contained in the oil in said oil receptacle, and means disposed within the oil space of said oil receptacle arranged to cool the oil therein.

25. An electric switch having an oil receptacle, relatively-movable switch-members contained in the oil in said oil receptacle, a cooling coil disposed within said 011 receptacle arranged tov cool the oil therein and means to circulate a cooling fluid through said cooling coil.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

GEORGE A. BURNHAM.

v WVitnesses:

T. T. GREENWOOD, H. B. DAVIS. 

